Underlayer composition and method of manufacturing a semiconductor device

ABSTRACT

A method of manufacturing a semiconductor device includes forming a photoresist underlayer over a semiconductor substrate. The underlayer includes a polymer having a photocleavable functional group. A photoresist layer is formed over the underlayer. The photoresist layer is selectively exposed to actinic radiation, and the selectively exposed photoresist layer is developed to form a photoresist pattern.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 16/952,023, filed Nov. 18, 2020, which claims priority to U.S.Provisional Patent Application No. 62/956,010, filed Dec. 31, 2019, theentire disclosure of each of which are incorporated herein by reference.

BACKGROUND

As consumer devices have gotten smaller and smaller in response toconsumer demand, the individual components of these devices havenecessarily decreased in size as well. Semiconductor devices, which makeup a major component of devices such as mobile phones, computer tablets,and the like, have been pressured to become smaller and smaller, with acorresponding pressure on the individual devices (e.g., transistors,resistors, capacitors, etc.) within the semiconductor devices to also bereduced in size.

One enabling technology that is used in the manufacturing processes ofsemiconductor devices is the use of photolithographic materials. Suchmaterials are applied to a surface of a layer to be patterned and thenexposed to an energy that has itself been patterned. Such an exposuremodifies the chemical and physical properties of the exposed regions ofthe photosensitive material. This modification, along with the lack ofmodification in regions of the photosensitive material that were notexposed, can be exploited to remove one region without removing theother.

However, as the size of individual devices has decreased, processwindows for photolithographic processing has become tighter and tighter.As such, advances in the field of photolithographic processing arenecessary to maintain the ability to scale down the devices, and furtherimprovements are needed in order to meet the desired design criteriasuch that the march towards smaller and smaller components may bemaintained.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 illustrates a process flow of manufacturing a semiconductordevice according to embodiments of the disclosure.

FIG. 2 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIGS. 3A and 3B show a process stage of a sequential operation accordingto embodiments of the disclosure.

FIG. 4 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 5 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 6 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIGS. 7A, 7B, 7C, and 7D illustrates polymers with photocleavablefunctional groups according to embodiments of the disclosure.

FIGS. 8A, 8B, 8C, 8D, 8E, and 8G illustrate polymers with photocleavablefunctional groups according to embodiments of the disclosure.

FIG. 9 illustrates components of underlayer compositions according toembodiments of the disclosure.

FIG. 10 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIGS. 11A and 11B show a process stage of a sequential operationaccording to embodiments of the disclosure.

FIG. 12 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 13 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 14 shows a process stage of a sequential operation according to anembodiment of the disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the disclosure. Specific embodiments or examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, dimensions of elements are not limited to thedisclosed range or values, but may depend upon process conditions and/ordesired properties of the device. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact. Variousfeatures may be arbitrarily drawn in different scales for simplicity andclarity.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The device may be otherwise oriented (rotated 90 degrees orat other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. In addition, the term“made of” may mean either “comprising” or “consisting of.”

Extreme ultraviolet (EUV) lithography to achieve sub-20 nm half-pitchresolution is under development for mass production for next generationsub 5 nm node. EUV lithography requires a high performance photoresistwith high sensitivity for cost reduction of the high-power exposuresource, and to provide good resolution of the image. Metallic resistshave been developed that provide high sensitivity and good resolution.However, pattern collapse and pattern scum may occur due to the reactionmechanism and higher interaction between the resist and a resistunderlayer. Embodiments of this disclosure provide improved adhesion ofthe photoresist pattern to the substrate thereby preventing patterncollapse while preventing pattern scum.

FIG. 1 illustrates a process flow 100 of manufacturing a semiconductordevice according to embodiments of the disclosure. A resist underlayercomposition is coated on a surface of a layer to be patterned or asubstrate 10 in operation S110, in some embodiments, to form a resistunderlayer 20, as shown in FIG. 2 . In some embodiments, the resistunderlayer 20 has a thickness ranging from about 2 nm to about 300 nm.In some embodiments, the resist underlayer has a thickness ranging fromabout 20 nm to about 100 nm. Then the resist underlayer 20 undergoes afirst baking operation S120 to evaporate solvents in the underlayercomposition in some embodiments. The underlayer 20 is baked at atemperature and time sufficient to cure and dry the underlayer 20. Insome embodiments, the underlayer is heated at a temperature of about 40°C. and 300° C. for about 10 seconds to about 10 minutes. In someembodiments, the underlayer is heated at a temperature ranging fromabout 80° C. to about 200° C. The first baking causes the underlayerpolymer composition to crosslink in some embodiments.

A resist layer composition is subsequently coated on a surface of theresist underlayer 20 in operation S130, in some embodiments, to form aresist layer 15, as shown in FIG. 2 . In some embodiments, the resistlayer 15 is a photoresist layer. Then the resist layer 15 undergoes asecond baking operation S140 (or pre-baking operation) to evaporatesolvents in the resist composition in some embodiments. The resist layer15 is baked at a temperature and time sufficient to cure and dry thephotoresist layer 15. In some embodiments, the resist layer is heated ata temperature of about 40° C. and 120° C. for about 10 seconds to about10 minutes. In some embodiments, the resist layer composition is coatedon the resist underlayer 20 prior to baking the resist underlayer 20,and the resist layer 15 and resist underlayer 20 are baked together in asingle baking operation to drive off solvents of both layers and causecrosslinking of the underlayer.

After the second (or pre-) baking operation S140 of the photoresistlayer 15, the photoresist layer 15 is selectively exposed to actinicradiation 45/97 (see FIGS. 3A and 3B) in operation S150. In someembodiments, the photoresist layer 15 is selectively exposed toultraviolet radiation. In some embodiments, the ultraviolet radiation isdeep ultraviolet radiation (DUV). In some embodiments, the ultravioletradiation is extreme ultraviolet (EUV) radiation. In some embodiments,the actinic radiation is an electron beam.

As shown in FIG. 3A, the exposure radiation 45 passes through aphotomask 30 before irradiating the photoresist layer 15 in someembodiments. In some embodiments, the photomask has a pattern to bereplicated in the photoresist layer 15. The pattern is formed by anopaque pattern 35 on the photomask substrate 40, in some embodiments.The opaque pattern 35 may be formed by a material opaque to ultravioletradiation, such as chromium, while the photomask substrate 40 is formedof a material that is transparent to ultraviolet radiation, such asfused quartz.

In some embodiments, the selective exposure of the photoresist layer 15to form exposed regions 50 and unexposed regions 52 is performed usingextreme ultraviolet lithography. In an extreme ultraviolet lithographyoperation a reflective photomask 65 is used to form the patternedexposure light in some embodiments, as shown in FIG. 3B. The reflectivephotomask 65 includes a low thermal expansion glass substrate 70, onwhich a reflective multilayer 75 of Si and Mo is formed. A capping layer80 and absorber layer 85 are formed on the reflective multilayer 75. Arear conductive layer 90 is formed on the back side of the low thermalexpansion glass substrate 70. In extreme ultraviolet lithography,extreme ultraviolet radiation 95 is directed towards the reflectivephotomask 65 at an incident angle of about 6°. A portion 97 of theextreme ultraviolet radiation is reflected by the Si/Mo multilayer 75towards the photoresist coated substrate 10, while the portion of theextreme ultraviolet radiation incident upon the absorber layer 85 isabsorbed by the photomask. In some embodiments, additional optics,including mirrors, are between the reflective photomask 65 and thephotoresist coated substrate.

The region of the photoresist layer exposed to radiation 50 undergoes achemical reaction thereby changing its solubility in a subsequentlyapplied developer relative to the region of the photoresist layer notexposed to radiation 52. In some embodiments, the portion of thephotoresist layer exposed to radiation 50 undergoes a crosslinkingreaction. In addition to causing the chemical reaction in thephotoresist layer 15, a portion of the radiation 45/97 also passesthrough the photoresist layer 15 and causes a reaction in the resistunderlayer 20. Portions of the resist underlayer exposed to theradiation 20 b have a different glass transition temperature (Tg),density, or porosity than portions of the resist underlayer not exposedto the radiation 20 a because of the radiation induced chemical reactionin the resist underlayer 20.

Next, the photoresist layer 15 undergoes a third baking (orpost-exposure bake (PEB)) in operation S160. In some embodiments, thephotoresist layer 15 is heated at a temperature of about 50° C. and 160°C. for about 20 seconds to about 120 seconds. The post-exposure bakingmay be used in order to assist in the generating, dispersing, andreacting of the acid/base/free radical generated from the impingement ofthe radiation 45/97 upon the photoresist layer 15 during the exposure.Such assistance helps to create or enhance chemical reactions, whichgenerate chemical differences between the exposed region 50 and theunexposed region 52 within the photoresist layer.

The selectively exposed photoresist layer is subsequently developed byapplying a developer to the selectively exposed photoresist layer inoperation S170. As shown in FIG. 4 , a developer 57 is supplied from adispenser 62 to the photoresist layer 15. In some embodiments, theunexposed portion 52 of the photoresist layer is removed by thedeveloper 57 forming a pattern of openings 55 in the photoresist layer15 to expose the underlayer 20 a, as shown in FIG. 5 .

In some embodiments, the pattern of openings 55 in the photoresist layer15 are extended through the underlayer 20 into the layer to be patternedor substrate 10 to create a pattern of openings 55′ in the substrate 10,thereby transferring the pattern in the photoresist layer 15 into thesubstrate 10, as shown in FIG. 6 . The pattern is extended into thesubstrate by etching, using one or more suitable etchants. In someembodiments, the etching operation remove the portions of the underlayer20 a between the photoresist pattern features 50. The photoresist layerpattern 50 is at least partially removed during the etching operation insome embodiments. In other embodiments, the photoresist layer pattern 50and the portion of the underlayer 20 b under the photoresist layerpattern are removed after etching the substrate 10 by using a suitablephotoresist stripper solvent or by a photoresist ashing operation.

In some embodiments, the substrate 10 includes a single crystallinesemiconductor layer on at least it surface portion. The substrate 10 mayinclude a single crystalline semiconductor material such as, but notlimited to Si, Ge, SiGe, GaAs, InSb, GaP, GaSb, InAlAs, InGaAs, GaSbP,GaAsSb and InP. In some embodiments, the substrate 10 is a silicon layerof an SOI (silicon-on insulator) substrate. In certain embodiments, thesubstrate 10 is made of crystalline Si.

The substrate 10 may include in its surface region, one or more bufferlayers (not shown). The buffer layers can serve to gradually change thelattice constant from that of the substrate to that of subsequentlyformed source/drain regions. The buffer layers may be formed fromepitaxially grown single crystalline semiconductor materials such as,but not limited to Si, Ge, GeSn, SiGe, GaAs, InSb, GaP, GaSb, InAlAs,InGaAs, GaSbP, GaAsSb, GaN, GaP, and InP. In an embodiment, the silicongermanium (SiGe) buffer layer is epitaxially grown on the siliconsubstrate 10. The germanium concentration of the SiGe buffer layers mayincrease from 30 atomic % for the bottom-most buffer layer to 70 atomic% for the top-most buffer layer.

In some embodiments, the substrate 10 includes one or more layers of atleast one metal, metal alloy, and metal nitride/sulfide/oxide/silicidehaving the formula MX_(a), where M is a metal and X is N, S, Se, O, Si,and a is from about 0.4 to about 2.5. In some embodiments, the substrate10 includes titanium, aluminum, cobalt, ruthenium, titanium nitride,tungsten nitride, tantalum nitride, and combinations thereof.

In some embodiments, the substrate 10 includes a dielectric having atleast a silicon or metal oxide or nitride of the formula MX_(b), where Mis a metal or Si, X is N or O, and b ranges from about 0.4 to about 2.5.In some embodiments, the substrate 10 includes silicon dioxide, siliconnitride, aluminum oxide, hafnium oxide, lanthanum oxide, andcombinations thereof.

Resist underlayers are made of polymer compositions disposed between theresist layer and the substrate to improve the adhesion of the resistlayer to the substrate in some embodiments. Embodiments of the presentdisclosure are directed to novel resist underlayers that allow controland tuning of glass transition temperature (Tg), density, or porosity ofthe resist underlayer. When the underlayer has a lower Tg than the postexposure bake temperature the exposed photoresist can infiltrate intothe underlayer during the post exposure bake process leading to residueremaining in the developed area. On the other hand, when the underlayerhas a higher Tg than the post exposure bake temperature, the pattern maycollapse after development because of poor adhesion between thephotoresist and the underlayer (surface property mismatch). While ahigher Tg is desirable to limit infiltration, high Tg can result inpattern collapse. Therefore, it is desirable to control theTg/density/porosity to achieve optimal results of inhibitinginfiltration and pattern collapse. In some embodiments, the underlayer20 is a bottom anti-reflective coating (BARC). In some embodiments, theBARC layer is an organic BARC, in other embodiments the BARC layer is aninorganic, such as a silicon-containing anti-reflective coating (SiARC)layer.

The underlayer according to embodiments of the disclosure has theability to control the Tg/density/porosity contrast between actinicradiation exposed portions of the underlayer and unexposed portions ofthe underlayer. In some embodiments, the underlayer 20 is a polymercomposition having a Tg higher than the post exposure bake (PEB)temperature. In some embodiments, the underlayer 20 has a Tg rangingfrom about 70° C. to about 220° C. The underlayer 20 is embedded withphotocleavable functional group that provides the underlayer 20 a bondcleavage function at the exposed areas. The bond cleavage function helpsto control the Tg/density/porosity. The Tg and density of the exposedarea in the exposed areas is reduced and the porosity is in the exposedareas is increased, thereby improving the Tg/density/porosity contrastbetween the exposed areas and the non-exposed areas of the underlayer.

The underlayer photocleavable functional groups can be embedded in theunderlayer polymer backbone (or main chain), underlayer polymer sidechain, or a cross-linker. Regardless of the position of thephotocleavable functional group, the differences in Tg, density, orporosity can be controlled by the amount of the cleavable functionalgroup, which is embedded in the polymer and/or cross-linker, and thepolymer molecular weight (MW). After exposure to actinic radiation, theunderlayer Tg decreases, the density decreases, and the porosityincreases in some embodiments. In some embodiments, the difference in Tgbetween actinic radiation exposed portions of the underlayer 20 b andunexposed portions 20 a ranges from about 1° C. to about 150° C. In someembodiments, the difference in Tg ranges from about 25° C. to about 100°C. In some embodiments, the difference in density between the actinicradiation exposed portions of the underlayer 20 b and the unexposedportions ranges from about 0.1 g/cm³ to about 1 g/cm³. In someembodiments, the difference in density ranges from about 0.2 g/cm³ toabout 0.8 g/cm³. In some embodiments, the difference in porosity betweenthe actinic radiation exposed portions of the underlayer 20 b than theunexposed portions ranges from about 1 to about 50%. In someembodiments, the difference in porosity ranges from about 5 to about35%. Tg, density, or porosity differences below the disclosed ranges mayprovide insufficient contrast between the actinic radiation exposed andunexposed portions and may result in an unacceptable level of patterncollapse. Tg, density, or porosity differences above the disclosedranges may result in an unacceptable amount of scum.

Embodiments of the present disclosure are illustrated in FIGS. 7A, 7B,7C, and 7D, where FIG. 7D is the key to FIGS. 7A, 7B, and 7C. As shownin FIG. 7A, the photocleavable group is embedded in the backbone of theunderlayer main polymer chain in some embodiments. In anotherembodiment, the photocleavable groups are embedded in the underlayerpolymer side chains, as shown in FIG. 7B. FIG. 7C illustrates theembodiment where the photocleavable groups are embedded in the crosslinker.

FIGS. 8A, 8B, and 8C illustrate the change in Tg of the underlayerpolymer before and after cleavage of the photocleavable groups byirradiation with actinic radiation according to an embodiment. FIG. 8Dis the key to FIGS. 8A, 8B, and 8C. In some embodiments, the actinicradiation is deep UV, such as a KrF or ArF laser irradiation. In otherembodiments, the actinic radiation is extreme ultraviolet (EUV)radiation, or an electron beam. The polymer in FIGS. 8A, 8B, and 8C is across linked poly(4-hydroxystyrene) (PHS) in some embodiments. As shownin FIG. 8A, the photocleavable group is embedded in the backbone of theunderlayer main polymer chain. Upon exposure to actinic radiation, thebackbone of the polymer chain is cleaved and the Tg is reduced. Inanother embodiment, the photocleavable groups are embedded in theunderlayer polymer side chains, as shown in FIG. 8B. Upon exposure toactinic radiation, the polymer side chain is cleaved and the Tg isreduced. FIG. 8C illustrates the embodiment where the photocleavablegroups are embedded in the cross linker. Upon exposure to actinicradiation, the cross linker is cleaved and the Tg is reduced.

In some embodiments, the photocleavable group is a polycarbonate, inother embodiments, the photocleavable group is a polysulfone. FIG. 8Fillustrates an example of a polysulfone having photocleavable groupsaccording to an embodiment of the disclosure. Polycarbonates andpolysulfones are cleaved when exposed to actinic radiation, such as deepUV, extreme UV, and electron beams. In some embodiments, differentfunctional groups are used in the same underlayer polymer composition,such as using both polysulfone and polycarbonate functional groups, totune the Tg, density, or porosity into a desired range. In someembodiments, the post exposure bake temperature and time are varied toadjust the Tg, density, or porosity of the underlayer.

FIG. 8G shows the variation of Tg of poly(4-hydroxystyrene) (4-PHS)according to an embodiment with molecular weight. Cleaving the 4-PHSreduces the molecular weight and the Tg. The Tg can be controlled by thecontrolling the molecular weight. As the molecular weight decreases, theTg starts decreasing from 176° C. to about 122° C. By controlling theamount of photocleavable groups in the crosslinked underlayer polymer,the Tg, density, or porosity of the underlayer can be controlled.

FIG. 9 illustrates some components of the underlayer compositionaccording to some embodiments of the disclosure. In some embodiments,the underlayer composition includes an organic polymer, including, butnot limited to polyhydroxystyrenes, polyacrylates, polymethacrylates,polyvinylphenols, polystyrenes, and copolymers thereof. In someembodiments, the organic polymer is a poly(4-hydroxystyrene), apoly(4-vinylphenol-co-methyl methacrylate) copolymer, and apoly(styrene)-b-poly(4-hydroxystyrene) copolymer, as illustrated in FIG.9 . In some embodiments, the underlayer composition includes, inorganicpolymers, such as a polysiloxane and polysiloxane derivatives. In someembodiments, the polysiloxane derivatives include functional groups,such as epoxy groups, amine groups, or thiol groups. The photocleavablefunctional groups are used with both the organic and the inorganicunderlayers in some embodiments. In some embodiments, photocleavablefunctional groups are oligomers or polymers with a number n of repeatingunits in the photocleavable functional groups ranging from about 2 toabout 500. Above about 500 repeating units in the photocleavable groupand the underlayer may suffer a decrease in performance.

In some embodiments, the underlayer 20 is formed by preparing anunderlayer coating composition of a polymer and a cross linker in asolvent. The solvent can be any suitable solvent for dissolving thepolymer and the cross linker. The underlayer coating composition isapplied over a substrate 10 or layer to be patterned, such as by spincoating. Then the underlayer composition is baked to dry the underlayerand cross link the polymer, as explained herein in reference to FIG. 1 .

In some embodiments, the thickness of the resist underlayer 20 rangesfrom about 2 nm to about 300 nm, and in other embodiments, the resistunderlayer thickness ranges from about 20 nm to about 100 nm. In someembodiments, the thickness of the resist underlayer 20 ranges from about40 nm to about 80 nm. Resist underlayer thicknesses less than thedisclosed ranges may be insufficient to provide adequate photoresistadhesion and anti-reflective properties. Resist underlayer thicknessesgreater than the disclosed ranges may be unnecessarily thick and may notprovide further improvement in resist layer adhesion and scum reduction.

The cross linker may be any suitable cross linker. The cross linkerreacts with a functional group on one of the main polymers and afunctional group on another one of the main polymers in order tocross-link and bond the two main polymer chains together. This bondingand cross-linking increases the molecular weight of the polymer productsof the cross-linking reaction and increases the overall density of theunderlayer.

In some embodiments the cross linker has the following structure:

In other embodiments, the cross linker has the following structure:

wherein C is carbon, n ranges from 1 to 15; A and B independentlyinclude a hydrogen atom, a hydroxyl group, a halide, an aromatic carbonring, or a straight or cyclic alkyl, alkoxyl/fluoro, alkyl/fluoroalkoxylchain having a carbon number of between 1 and 12, and each carbon Ccontains A and B; a first terminal carbon C at a first end of a carbon Cchain includes X and a second terminal carbon C at a second end of thecarbon chain includes Y, wherein X and Y independently include an aminegroup, a thiol group, a hydroxyl group, an isopropyl alcohol group, oran isopropyl amine group, except when n=1 then X and Y are bonded to thesame carbon C. Specific examples of materials that may be used as thecross-linking agent include the following:

Alternatively, instead of or in addition to the cross linker being addedto the resist underlayer composition, a coupling reagent is added insome embodiments, in which the coupling reagent is added in addition tothe cross linker agent. The coupling reagent assists the cross-linkingreaction by reacting with the functional groups on the polymer beforethe cross linker, allowing for a reduction in the reaction energy of thecross-linking reaction and an increase in the rate of reaction. Thebonded coupling reagent then reacts with the cross linker agent, therebycoupling the cross-linker to the polymers.

In some embodiments, the coupling reagent has the following structure:

where R is a carbon atom, a nitrogen atom, a sulfur atom, or an oxygenatom; M includes a chlorine atom, a bromine atom, an iodine atom, —NO₂;—SO₃—; —H—; —CN; —NCO, —OCN; —CO₂—; —OH; —OR*, —OC(O)CR*; —SR*,—SO₂N(R*)₂; —SO₂R*; SOR*; —OC(O)R*; —C(O)OR*; —C(O)R*; —Si(OR*)₃;—Si(R*)₃; epoxy groups, or the like; and R* is a substituted orunsubstituted C1-C12 alkyl, C1-C12 aryl, C1-C12 aralkyl, or the like.Specific examples of materials used as the coupling reagent in someembodiments include the following:

In some embodiments, the photoresist layer 15 is a photosensitive layerthat is patterned by exposure to actinic radiation. Typically, thechemical properties of the photoresist regions struck by incidentradiation change in a manner that depends on the type of photoresistused. Photoresist layers 15 are either positive tone resists or negativetone resists. A positive tone resist refers to a photoresist materialthat when exposed to radiation, such as UV light, becomes soluble in adeveloper, while the region of the photoresist that is non-exposed (orexposed less) is insoluble in the developer. A negative tone resist, onthe other hand, refers to a photoresist material that when exposed toradiation becomes insoluble in the developer, while the region of thephotoresist that is non-exposed (or exposed less) is soluble in thedeveloper. The region of a negative resist that becomes insoluble uponexposure to radiation may become insoluble due to a cross-linkingreaction caused by the exposure to radiation.

Whether a resist is a positive tone or negative tone may depend on thetype of developer used to develop the resist. For example, some positivetone photoresists provide a positive pattern, (i.e.—the exposed regionsare removed by the developer), when the developer is an aqueous-baseddeveloper, such as a tetramethylammonium hydroxide (TMAH) solution. Onthe other hand, the same photoresist provides a negative pattern(i.e.—the unexposed regions are removed by the developer) when thedeveloper is an organic solvent. Further, in some negative tonephotoresists developed with the TMAH solution, the unexposed regions ofthe photoresist are removed by the TMAH, and the exposed regions of thephotoresist, that undergo cross-linking upon exposure to actinicradiation, remain on the substrate after development.

In some embodiments, resist compositions according to embodiments of thedisclosure, such as a photoresist, include a polymer or a polymerizablemonomer or oligomer along with one or more photoactive compounds (PACs).In some embodiments, the concentration of the polymer, monomer, oroligomer ranges from about 1 wt. % to about 75 wt. % based on the totalweight of the resist composition. In other embodiments, theconcentration of the polymer, monomer, or oligomer ranges from about 5wt. % to about 50 wt. %. At concentrations of the polymer, monomer, oroligomer below the disclosed ranges the polymer, monomer, or oligomerhas negligible effect on the resist performance. At concentrations abovethe disclosed ranges, there is no substantial improvement in resistperformance or there is degradation in the formation of consistentresist layers.

In some embodiments, the polymerizable monomer or oligomer includes anacrylic acid, an acrylate, a hydroxystyrene, or an alkylene. In someembodiments, the polymer includes a hydrocarbon structure (such as analicyclic hydrocarbon structure) that contains one or more groups thatwill decompose (e.g., acid labile groups) or otherwise react when mixedwith acids, bases, or free radicals generated by the PACs (as furtherdescribed below). In some embodiments, the hydrocarbon structureincludes a repeating unit that forms a skeletal backbone of the polymerresin. This repeating unit may include acrylic esters, methacrylicesters, crotonic esters, vinyl esters, maleic diesters, fumaricdiesters, itaconic diesters, (meth)acrylonitrile, (meth)acrylamides,styrenes, vinyl ethers, combinations of these, or the like.

Specific structures that are utilized for the repeating unit of thehydrocarbon structure in some embodiments, include one or more of methylacrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butylacrylate, isobutyl acrylate, tert-butyl acrylate, n-hexyl acrylate,2-ethylhexyl acrylate, acetoxyethyl acrylate, phenyl acrylate,2-hydroxyethyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethylacrylate, 2-(2-methoxyethoxy)ethyl acrylate, cyclohexyl acrylate, benzylacrylate, 2-alkyl-2-adamantyl (meth)acrylate ordialkyl(1-adamantyl)methyl (meth)acrylate, methyl methacrylate, ethylmethacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butylmethacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-hexylmethacrylate, 2-ethylhexyl methacrylate, acetoxyethyl methacrylate,phenyl methacrylate, 2-hydroxyethyl methacrylate, 2-methoxyethylmethacrylate, 2-ethoxyethyl methacrylate, 2-(2-methoxyethoxy)ethylmethacrylate, cyclohexyl methacrylate, benzyl methacrylate,3-chloro-2-hydroxypropyl methacrylate, 3-acetoxy-2-hydroxypropylmethacrylate, 3-chloroacetoxy-2-hydroxypropyl methacrylate, butylcrotonate, hexyl crotonate, or the like. Examples of the vinyl estersinclude vinyl acetate, vinyl propionate, vinyl butylate, vinylmethoxyacetate, vinyl benzoate, dimethyl maleate, diethyl maleate,dibutyl maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate,dimethyl itaconate, diethyl itaconate, dibutyl itaconate, acrylamide,methyl acrylamide, ethyl acrylamide, propyl acrylamide, n-butylacrylamide, tert-butyl acrylamide, cyclohexyl acrylamide, 2-methoxyethylacrylamide, dimethyl acrylamide, diethyl acrylamide, phenyl acrylamide,benzyl acrylamide, methacrylamide, methyl methacrylamide, ethylmethacrylamide, propyl methacrylamide, n-butyl methacrylamide,tert-butyl methacrylamide, cyclohexyl methacrylamide, 2-methoxyethylmethacrylamide, dimethyl methacrylamide, diethyl methacrylamide, phenylmethacrylamide, benzyl methacrylamide, methyl vinyl ether, butyl vinylether, hexyl vinyl ether, methoxyethyl vinyl ether, dimethylaminoethylvinyl ether, or the like. Examples of styrenes include styrene, methylstyrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropylstyrene, butyl styrene, methoxy styrene, butoxy styrene, acetoxystyrene, hydroxy styrene, chloro styrene, dichloro styrene, bromostyrene, vinyl methyl benzoate, a-methyl styrene, maleimide,vinylpyridine, vinylpyrrolidone, vinylcarbazole, combinations of these,or the like.

In some embodiments, the polymer is a polyhydroxystyrene, a polymethylmethacrylate, or a polyhydroxystyrene-t-butyl acrylate, e.g. —

In some embodiments, the repeating unit of the hydrocarbon structurealso has either a monocyclic or a polycyclic hydrocarbon structuresubstituted into it, or the monocyclic or polycyclic hydrocarbonstructure is the repeating unit, in order to form an alicyclichydrocarbon structure. Specific examples of monocyclic structures insome embodiments include bicycloalkane, tricycloalkane,tetracycloalkane, cyclopentane, cyclohexane, or the like. Specificexamples of polycyclic structures in some embodiments includeadamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane,or the like.

The group which will decompose, otherwise known as a leaving group or,in some embodiments in which the PAC is a photoacid generator, an acidlabile group, is attached to the hydrocarbon structure so that, it willreact with the acids/bases/free radicals generated by the PACs duringexposure. In some embodiments, the group which will decompose is acarboxylic acid group, a fluorinated alcohol group, a phenolic alcoholgroup, a sulfonic group, a sulfonamide group, a sulfonylimido group, an(alkylsulfonyl) (alkylcarbonyl)methylene group, an(alkylsulfonyl)(alkyl-carbonyl)imido group, abis(alkylcarbonyl)methylene group, a bis(alkylcarbonyl)imido group, abis(alkylsylfonyl)methylene group, a bis(alkylsulfonyl)imido group, atris(alkylcarbonyl methylene group, a tris(alkylsulfonyl)methylenegroup, combinations of these, or the like. Specific groups that are usedfor the fluorinated alcohol group include fluorinated hydroxyalkylgroups, such as a hexafluoroisopropanol group in some embodiments.Specific groups that are used for the carboxylic acid group includeacrylic acid groups, methacrylic acid groups, or the like.

In some embodiments, the polymer also includes other groups attached tothe hydrocarbon structure that help to improve a variety of propertiesof the polymerizable resin. For example, inclusion of a lactone group tothe hydrocarbon structure assists to reduce the amount of line edgeroughness after the photoresist has been developed, thereby helping toreduce the number of defects that occur during development. In someembodiments, the lactone groups include rings having five to sevenmembers, although any suitable lactone structure may alternatively beused for the lactone group.

In some embodiments, the polymer includes groups that can assist inincreasing the adhesiveness of the photoresist layer 15 to underlyingstructures (e.g., substrate 10). Polar groups may be used to helpincrease the adhesiveness. Suitable polar groups include hydroxylgroups, cyano groups, or the like, although any suitable polar groupmay, alternatively, be used.

Optionally, the polymer includes one or more alicyclic hydrocarbonstructures that do not also contain a group, which will decompose insome embodiments. In some embodiments, the hydrocarbon structure thatdoes not contain a group which will decompose includes structures suchas 1-adamantyl(meth)acrylate, tricyclodecanyl (meth)acrylate, cyclohexyl(methacrylate), combinations of these, or the like.

In some embodiments, such as when EUV radiation is used, the photoresistcompositions according to the present disclosure are metal-containingresists. The metal-containing resists include metallic cores complexedwith one or more ligands in a solvent. In some embodiments, the resistincludes metal particles. In some embodiments, the metal particles arenanoparticles. As used herein, nanoparticles are particles having anaverage particle size between about 1 nm and about 20 nm. In someembodiments, the metallic cores, including from 1 to about 18 metalparticles, are complexed with one or more organic ligands in a solvent.In some embodiments, the metallic cores include 3, 6, 9, or more metalnanoparticles complexed with one or more organic ligands in a solvent.

In some embodiments, the metal particle is one or more of titanium (Ti),zinc (Zn), zirconium (Zr), nickel (Ni), cobalt (Co), manganese (Mn),copper (Cu), iron (Fe), strontium (Sr), tungsten (W), vanadium (V),chromium (Cr), tin (Sn), hafnium (Hf), indium (In), cadmium (Cd),molybdenum (Mo), tantalum (Ta), niobium (Nb), aluminum (Al), cesium(Cs), barium (Ba), lanthanum (La), cerium (Ce), silver (Ag), antimony(Sb), combinations thereof, or oxides thereof. In some embodiments, themetal particles include one or more selected from the group consistingof Ce, Ba, La, Ce, In, Sn, Ag, Sb, and oxides thereof.

In some embodiments, the metal nanoparticles have an average particlesize between about 2 nm and about 5 nm. In some embodiments, the amountof metal nanoparticles in the resist composition ranges from about 0.5wt. % to about 15 wt. % based on the weight of the nanoparticles and thesolvent. In some embodiments, the amount of nanoparticles in the resistcomposition ranges from about 5 wt. % to about 10 wt. % based on theweight of the nanoparticles and the solvent. In some embodiments, theconcentration of the metal particles ranges from 1 wt. % to 7 wt. %based on the weight of the solvent and the metal particles. Below about0.5 wt. % metal nanoparticles, the resist coating is too thin. Aboveabout 15 wt. % metal nanoparticles, the resist coating is too thick andviscous.

In some embodiments, the metallic core is complexed by a ligand, whereinthe ligand includes branched or unbranched, cyclic or non-cyclic,saturated organic groups, including C1-C7 alkyl groups or C1-C7fluoroalkyl groups. The C1-C7 alkyl groups or C1-C7 fluoroalkyl groupsinclude one or more substituents selected from the group consisting of—CF₃, —SH, —OH, ═O, —S—, —P—, —PO₂, —C(═O)SH, —C(═O)OH, —C(═O)O—, —O—,—N—, —C(═O)NH, —SO₂OH, —SO₂SH, —SOH, and —SO₂—. In some embodiments, theligand includes one or more substituents selected from the groupconsisting of —CF₃, —OH, —SH, and —C(═O)OH substituents.

In some embodiments, the ligand is a carboxylic acid or sulfonic acidligand. For example, in some embodiments, the ligand is a methacrylicacid. In some embodiments, the metal particles are nanoparticles, andthe metal nanoparticles are complexed with ligands including aliphaticor aromatic groups. The aliphatic or aromatic groups may be unbranchedor branched with cyclic or noncyclic saturated pendant groups containing1-9 carbons, including alkyl groups, alkenyl groups, and phenyl groups.The branched groups may be further substituted with oxygen or halogen.In some embodiments, each metal particle is complexed by 1 to 25 ligandunits. In some embodiments, each metal particle is complexed by 3 to 18ligand units.

In some embodiments, the resist composition includes about 0.1 wt. % toabout 20 wt. % of the ligands based on the total weight of the resistcomposition. In some embodiments, the resist includes about 1 wt. % toabout 10 wt. % of the ligands. In some embodiments, the ligandconcentration is about 10 wt. % to about 40 wt. % based on the weight ofthe metal particles and the weight of the ligands. Below about 10 wt. %,ligand, the organometallic photoresist does not function well. Aboveabout 40 wt. %, ligand, it is difficult to form a consistent photoresistlayer. In some embodiments, the ligand(s) is dissolved at about a 5 wt.% to about 10 wt. % weight range in a coating solvent, such as propyleneglycol methyl ether acetate (PGMEA) based on the weight of the ligand(s)and the solvent.

In some embodiments, the copolymers and the PACs, along with any desiredadditives or other agents, are added to the solvent for application.Once added, the mixture is then mixed in order to achieve a homogenouscomposition throughout the photoresist to ensure that there are nodefects caused by uneven mixing or nonhomogeneous composition of thephotoresist. Once mixed together, the photoresist may either be storedprior to its usage or used immediately.

The solvent can be any suitable solvent. In some embodiments, thesolvent is one or more selected from propylene glycol methyl etheracetate (PGMEA), propylene glycol monomethyl ether (PGME),1-ethoxy-2-propanol (PGEE), γ-butyrolactone (GBL), cyclohexanone (CHN),ethyl lactate (EL), methanol, ethanol, propanol, n-butanol, acetone,dimethylformamide (DMF), isopropanol (IPA), tetrahydrofuran (THF),methyl isobutyl carbinol (MIBC), n-butyl acetate (nBA), and 2-heptanone(MAK).

Some embodiments of the photoresist include one or more photoactivecompounds (PACs). The PACs are photoactive components, such as photoacidgenerators (PAG), photobase (PBG) generators, photo decomposable bases(PDB), free-radical generators, or the like. The PACs may bepositive-acting or negative-acting. In some embodiments in which thePACs are a photoacid generator, the PACs include halogenated triazines,onium salts, diazonium salts, aromatic diazonium salts, phosphoniumsalts, sulfonium salts, iodonium salts, imide sulfonate, oximesulfonate, diazodisulfone, disulfone, o-nitrobenzylsulfonate, sulfonatedesters, halogenated sulfonyloxy dicarboximides, diazodisulfones,α-cyanooxyamine-sulfonates, imidesulfonates, ketodiazosulfones,sulfonyldiazoesters, 1,2-di(arylsulfonyl)hydrazines, nitrobenzyl esters,and the s-triazine derivatives, combinations of these, or the like.

Specific examples of photoacid generators includeα-(trifluoromethylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarb-o-ximide(MDT), N-hydroxy-naphthalimide (DDSN), benzoin tosylate,t-butylphenyl-α-(p-toluenesulfonyloxy)-acetate andt-butyl-α-(p-toluenesulfonyloxy)-acetate, triarylsulfonium anddiaryliodonium hexafluoroantimonates, hexafluoroarsenates,trifluoromethanesulfonates, iodonium perfluorooctanesulfonate,N-camphorsulfonyloxynaphthalimide,N-pentafluorophenylsulfonyloxynaphthalimide, ionic iodonium sulfonatessuch as diaryl iodonium (alkyl or aryl)sulfonate andbis-(di-t-butylphenyl)iodonium camphanylsulfonate,perfluoroalkanesulfonates such as perfluoropentanesulfonate,perfluorooctanesulfonate, perfluoromethanesulfonate, aryl (e.g., phenylor benzyl)triflates such as triphenylsulfonium triflate orbis-(t-butylphenyl)iodonium triflate; pyrogallol derivatives (e.g.,trimesylate of pyrogallol), trifluoromethanesulfonate esters ofhydroxyimides, α,α′-bis-sulfonyl-diazomethanes, sulfonate esters ofnitro-substituted benzyl alcohols, naphthoquinone-4-diazides, alkyldisulfones, or the like.

In some embodiments in which the PACs are free-radical generators, thePACs include n-phenylglycine; aromatic ketones, including benzophenone,N,N′-tetramethyl-4,4′-diaminobenzophenone,N,N′-tetraethyl-4,4′-diaminobenzophenone,4-methoxy-4′-dimethylaminobenzo-phenone,3,3′-dimethyl-4-methoxybenzophenone,p,p′-bis(dimethylamino)benzo-phenone,p,p′-bis(diethylamino)-benzophenone; anthraquinone,2-ethylanthraquinone; naphthaquinone; and phenanthraquinone; benzoinsincluding benzoin, benzoinmethylether, benzoinisopropylether,benzoin-n-butylether, benzoin-phenylether, methylbenzoin andethylbenzoin; benzyl derivatives, including dibenzyl,benzyldiphenyldisulfide, and benzyldimethylketal; acridine derivatives,including 9-phenylacridine, and 1,7-bis(9-acridinyl)heptane;thioxanthones, including 2-chlorothioxanthone, 2-methylthioxanthone,2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, and2-isopropylthioxanthone; acetophenones, including1,1-dichloroacetophenone, p-t-butyldichloro-acetophenone,2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, and2,2-dichloro-4-phenoxyacetophenone; 2,4,5-triarylimidazole dimers,including 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer,2-(o-chlorophenyl)-4,5-di-(m-methoxyphenyl imidazole dimer,2-(o-fluorophenyl)-4,5-diphenylimidazole dimer,2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer,2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer,2,4-di(p-methoxyphenyl)-5-phenylimidazole dimer,2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazole dimer and2-(p-methylmercaptophenyl)-4,5-diphenylimidazole dimmer; combinations ofthese, or the like.

As one of ordinary skill in the art will recognize, the chemicalcompounds listed herein are merely intended as illustrated examples ofthe PACs and are not intended to limit the embodiments to only thosePACs specifically described. Rather, any suitable PAC may be used, andall such PACs are fully intended to be included within the scope of thepresent embodiments.

In some embodiments, a cross linker is added to the photoresist. Thecross linker reacts with one group from one of the hydrocarbonstructures in the polymer resin and also reacts with a second group froma separate one of the hydrocarbon structures in order to cross-link andbond the two hydrocarbon structures together. This bonding andcross-linking increases the molecular weight of the polymer products ofthe cross-linking reaction and increases the overall linking density ofthe photoresist. Such an increase in density and linking density helpsto improve the resist pattern.

In some embodiments the cross linker has the following structure:

In other embodiments, the cross-linking agent has the followingstructure:

wherein C is carbon, n ranges from 1 to 15; A and B independentlyinclude a hydrogen atom, a hydroxyl group, a halide, an aromatic carbonring, or a straight or cyclic alkyl, alkoxyl/fluoro, alkyl/fluoroalkoxylchain having a carbon number of between 1 and 12, and each carbon Ccontains A and B; a first terminal carbon C at a first end of a carbon Cchain includes X and a second terminal carbon C at a second end of thecarbon chain includes Y, wherein X and Y independently include an aminegroup, a thiol group, a hydroxyl group, an isopropyl alcohol group, oran isopropyl amine group, except when n=1 then X and Y are bonded to thesame carbon C. Specific examples of materials that may be used as thecross linker include the following:

Alternatively, instead of or in addition to the cross linker being addedto the photoresist composition, a coupling reagent is added in someembodiments, in which the coupling reagent is added in addition to thecross-linking agent. The coupling reagent assists the cross-linkingreaction by reacting with the groups on the hydrocarbon structure in thepolymer resin before the cross-linking reagent, allowing for a reductionin the reaction energy of the cross-linking reaction and an increase inthe rate of reaction. The bonded coupling reagent then reacts with thecross-linking agent, thereby coupling the cross linker to the polymerresin.

Alternatively, in some embodiments in which the coupling reagent isadded to the photoresist composition without the cross linker, thecoupling reagent is used to couple one group from one of the hydrocarbonstructures in the polymer resin to a second group from a separate one ofthe hydrocarbon structures in order to cross-link and bond the twopolymers together. However, in such an embodiment the coupling reagent,unlike the cross linker, does not remain as part of the polymer, andonly assists in bonding one hydrocarbon structure directly to anotherhydrocarbon structure.

In some embodiments, the coupling reagent has the following structure:

where R is a carbon atom, a nitrogen atom, a sulfur atom, or an oxygenatom; M includes a chlorine atom, a bromine atom, an iodine atom, —NO₂;—SO₃—; —H—; —CN; —NCO, —OCN; —CO₂—; —OH; —OR*, —OC(O)CR*; —SR*,—SO₂N(R*)₂; —SO₂R*; SOR*; —OC(O)R*; —C(O)OR*; —C(O)R*; —Si(OR*)₃;—Si(R*)₃; epoxy groups, or the like; and R* is a substituted orunsubstituted C1-C12 alkyl, C1-C12 aryl, C1-C12 aralkyl, or the like.Specific examples of materials used as the coupling reagent in someembodiments include the following:

The individual components of the photoresist are placed into a solventin order to aid in the mixing and dispensing of the photoresist. To aidin the mixing and dispensing of the photoresist, the solvent is chosenat least in part based upon the materials chosen for the polymer resinas well as the PACs. In some embodiments, the solvent is chosen suchthat the polymer resin and the PACs can be evenly dissolved into thesolvent and dispensed upon the layer to be patterned.

In some embodiments, a quencher is added to the photoresist in someembodiments to inhibit diffusion of the generated acids/bases/freeradicals within the photoresist. The quencher improves the resistpattern configuration as well as the stability of the photoresist overtime.

Another additive added to the photoresist in some embodiments is astabilizer, which assists in preventing undesired diffusion of the acidsgenerated during exposure of the photoresist.

Another additive added to the photoresist in some embodiments is adissolution inhibitor to help control dissolution of the photoresistduring development.

A coloring agent is another additive added to the photoresist in someembodiments of the photoresist. The coloring agent observers examine thephotoresist and find any defects that may need to be remedied prior tofurther processing.

Surface leveling agents are added to the photoresist in some embodimentsto assist a top surface of the photoresist to be level, so thatimpinging light will not be adversely modified by an unlevel surface.

In some embodiments, the polymer resin and the PACs, along with anydesired additives or other agents, are added to the solvent forapplication. Once added, the mixture is then mixed in order to achieve ahomogenous composition throughout the photoresist to ensure that thereare no defects caused by uneven mixing or nonhomogenous composition ofthe photoresist. Once mixed together, the photoresist may either bestored prior to its usage or used immediately.

Once ready, the photoresist is applied onto the underlayer 20, as shownin FIG. 2 , to form a photoresist layer 15. In some embodiments, thephotoresist is applied using a process such as a spin-on coatingprocess, a dip coating method, an air-knife coating method, a curtaincoating method, a wire-bar coating method, a gravure coating method, alamination method, an extrusion coating method, combinations of these,or the like. In some embodiments, the photoresist layer 15 thicknessranges from about 10 nm to about 300 nm.

After the photoresist layer 15 has been applied to the substrate 10, apre-exposure bake of the photoresist layer is performed in someembodiments to cure and dry the photoresist prior to radiation exposure(see FIG. 1 ). The curing and drying of the photoresist layer 15 removesthe solvent component while leaving behind the photoresist polymer, thePACs, the cross linker, and the other chosen additives. In someembodiments, the pre-baking is performed at a temperature suitable toevaporate the solvent, such as between about 50° C. and 120° C.,although the precise temperature depends upon the materials chosen forthe photoresist. The pre-baking is performed for a time sufficient tocure and dry the photoresist layer, such as between about 10 seconds toabout 10 minutes.

FIGS. 3A and 3B illustrate selective exposures of the photoresist layer15 and underlayer to form exposed regions 50 and 20 b, respectively, andunexposed regions 52 and 20 a, respectively. In some embodiments, theexposure to radiation is carried out by placing the photoresist coatedsubstrate in a photolithography tool. The photolithography tool includesa photomask 30/65, optics, an exposure radiation source to provide theradiation 45/97 for exposure, and a movable stage for supporting andmoving the substrate under the exposure radiation.

In some embodiments, the radiation source (not shown) supplies radiation45, 97, such as ultraviolet light, to the photoresist layer 15 in orderto induce a reaction of the PACs, which in turn reacts with the polymerresin to chemically alter those regions of the photoresist layer towhich the radiation 45, 97 impinges, and to cleave the photocleavablegroups in the underlayer 20. In some embodiments, the radiation iselectromagnetic radiation, such as g-line (wavelength of about 436 nm),i-line (wavelength of about 365 nm), ultraviolet radiation, deepultraviolet radiation, extreme ultraviolet, electron beams, or the like.In some embodiments, the radiation source is selected from the groupconsisting of a mercury vapor lamp, xenon lamp, carbon arc lamp, a KrFexcimer laser light (wavelength of 248 nm), an ArF excimer laser light(wavelength of 193 nm), an F₂ excimer laser light (wavelength of 157nm), or a CO₂ laser-excited Sn plasma (extreme ultraviolet, wavelengthof 13.5 nm).

In some embodiments, optics (not shown) are used in the photolithographytool to expand, reflect, or otherwise control the radiation before orafter the radiation 45/97 is patterned by the photomask 30/65. In someembodiments, the optics include one or more lenses, mirrors, filters,and combinations thereof to control the radiation 45/97 along its path.

In an embodiment, the patterned radiation 97 is extreme ultravioletlight having a wavelength of about 13.5 nm, the PAC is a photoacidgenerator, and a cross linker is used. The patterned radiation 97impinges upon the photoacid generator, and the photoacid generatorabsorbs the impinging patterned radiation 97. This absorption initiatesthe photoacid generator to generate a proton (e.g., a H⁺ atom) withinthe photoresist layer 15. When the proton impacts the carboxylic acidgroup on the hydrocarbon structure, the proton reacts with thecarboxylic acid group, chemically altering the carboxylic acid group andaltering the properties of the polymer resin in general. The carboxylicacid group then reacts with the cross linker in some embodiments tocross-link with other polymer resins within the exposed region of thephotoresist layer 15. In addition, the patterned radiation 97 impingesupon the photocleavable functional groups embedded in the underlayerpolymer causing the underlayer polymer to cleave with accompanyingdecrease in molecular weight, glass transition temperature, and density,and increase in porosity.

After the photoresist layer 15 and underlayer 20 have been exposed tothe exposure radiation 45/97, a post-exposure baking is performed insome embodiments to assist in the generating, dispersing, reacting ofthe acid/base/free radical generated from the impingement of theradiation 45/97 upon the PACs during the exposure by advancing across-linking reaction occurs in the exposed areas of the photoresistlayer, and the cleaving of the photocleavable functional groups. In someembodiments, the post-exposure baking occurs at temperatures rangingfrom about 50° C. to about 160° C. for a period of between about 20seconds and about 120 seconds.

In some embodiments, the photoresist developer 57 includes a solvent,and an acid or a base. In some embodiments, the concentration of thesolvent is from about 60 wt. % to about 99 wt. % based on the totalweight of the photoresist developer. The acid or base concentration isfrom about 0.001 wt. % to about 20 wt. % based on the total weight ofthe photoresist developer. In certain embodiments, the acid or baseconcentration in the developer is from about 0.01 wt. % to about 15 wt.% based on the total weight of the photoresist developer.

In some embodiments, the developer 57 is applied to the photoresistlayer 15 using a spin-on process. In the spin-on process, the developer57 is applied to the photoresist layer 15 from above the photoresistlayer 15 while the photoresist-coated substrate is rotated, as shown inFIG. 4 . In some embodiments, the developer 57 is supplied at a rate ofbetween about 5 ml/min and about 800 ml/min, while the photoresistcoated substrate 10 is rotated at a speed of between about 100 rpm andabout 2000 rpm. In some embodiments, the developer is at a temperatureof between about 10° C. and about 80° C. The development operationcontinues for between about 30 seconds to about 10 minutes in someembodiments.

While the spin-on operation is one suitable method for developing thephotoresist layer 15 after exposure, it is intended to be illustrativeand is not intended to limit the embodiment. Rather, any suitabledevelopment operations, including dip processes, puddle processes, andspray-on methods, may alternatively be used. All such developmentoperations are included within the scope of the embodiments.

During the development process, the developer 57 dissolves theradiation-unexposed regions 52 of the cross-linked negative resist,exposing the surface of the underlayer 20, as shown in FIG. 5 , andleaving behind well-defined exposed photoresist regions 50, havingimproved definition than provided by conventional negative photoresistphotolithography.

After the developing operation S170, remaining developer is removed fromthe patterned photoresist covered substrate. The remaining developer isremoved using a spin-dry process in some embodiments, although anysuitable removal technique may be used. After the photoresist layer 15is developed, and the remaining developer is removed, additionalprocessing is performed while the patterned photoresist layer 50 is inplace. For example, an etching operation, using dry or wet etching, isperformed in some embodiments, to transfer the pattern of thephotoresist layer 50 through the underlayer 20 to the underlyingsubstrate 10, forming recesses 55′ as shown in FIG. 6 . The underlayer20 and the substrate 10 have a different etch resistance than thephotoresist layer 15. In some embodiments, the etchant is more selectiveto the underlayer 20 and substrate 10 than the photoresist layer 15. Insome embodiments, a different etchant or etching parameters is used toetch the non-photocleaved portions of the underlayer 20 a than to etchthe substrate 10.

In some embodiments, a layer to be patterned 60 is disposed over thesubstrate prior to forming the underlayer 20, as shown in FIG. 10 . Insome embodiments, the layer to be patterned 60 is a metallization layeror a dielectric layer, such as a passivation layer, disposed over ametallization layer. In embodiments where the layer to be patterned 60is a metallization layer, the layer to be patterned 60 is formed of aconductive material using metallization processes, and metal depositiontechniques, including chemical vapor deposition, atomic layerdeposition, and physical vapor deposition (sputtering). Likewise, if thelayer to be patterned 60 is a dielectric layer, the layer to bepatterned 60 is formed by dielectric layer formation techniques,including thermal oxidation, chemical vapor deposition, atomic layerdeposition, and physical vapor deposition.

The photoresist layer 15 and resist underlayer 20 are subsequentlyselectively exposed to actinic radiation 45/97 to form exposed regions50 and 20 b and unexposed regions 52 and 20 a, in the photoresist layerand underlayer, respectively, as shown in FIGS. 11A and 11B, anddescribed herein in relation to FIGS. 3A and 3B. As explained herein thephotoresist is a negative photoresist, wherein polymer crosslinkingoccurs in the exposed regions 50 in some embodiments.

As shown in FIG. 12 , the unexposed photoresist regions 52 are developedby dispensing developer 57 from a dispenser 62 to form a pattern ofphotoresist openings 55, as shown in FIG. 13 . The development operationis similar to that explained with reference to FIGS. 4 and 5 , herein.

Then as shown in FIG. 14 , the pattern 55 in the photoresist layer 15 istransferred through the unexposed portion of the resist underlayer 20 ato the layer to be patterned 60 using an etching operation and thephotoresist layer 15 and exposed portion of the resist underlayer 20 bare removed, as explained with reference to FIG. 6 to form pattern 55″in the layer to be patterned 60.

Other embodiments include other operations before, during, or after theoperations described above. In some embodiments, the disclosed methodsinclude forming semiconductor devices, including fin field effecttransistor (FinFET) structures. In some embodiments, a plurality ofactive fins are formed on the semiconductor substrate. Such embodiments,further include etching the substrate through the openings of apatterned hard mask to form trenches in the substrate; filling thetrenches with a dielectric material; performing a chemical mechanicalpolishing (CMP) process to form shallow trench isolation (STI) features;and epitaxy growing or recessing the STI features to form fin-likeactive regions. In some embodiments, one or more gate electrodes areformed on the substrate. Some embodiments include forming gate spacers,doped source/drain regions, contacts for gate/source/drain features,etc. In other embodiments, a target pattern is formed as metal lines ina multilayer interconnection structure. For example, the metal lines maybe formed in an inter-layer dielectric (ILD) layer of the substrate,which has been etched to form a plurality of trenches. The trenches maybe filled with a conductive material, such as a metal; and theconductive material may be polished using a process such as chemicalmechanical planarization (CMP) to expose the patterned ILD layer,thereby forming the metal lines in the ILD layer. The above arenon-limiting examples of devices/structures that can be made and/orimproved using the method described herein.

In some embodiments, active components such diodes, field-effecttransistors (FETs), metal-oxide semiconductor field effect transistors(MOSFET), complementary metal-oxide semiconductor (CMOS) transistors,bipolar transistors, high voltage transistors, high frequencytransistors, FinFETs, other three-dimensional (3D) FETs, other memorycells, and combinations thereof are formed, according to embodiments ofthe disclosure.

The novel underlayer compositions and semiconductor device manufacturingmethods according to the present disclosure provide higher semiconductordevice feature resolution and density at higher wafer exposurethroughput with reduced defects in a higher efficiency process thanconventional exposure techniques. Embodiments of the disclosure provideimproved adhesion of the photoresist pattern to the substrate therebypreventing pattern collapse while preventing pattern scum.

An embodiment of the disclosure is a method of manufacturing asemiconductor device, including forming a photoresist underlayer over asemiconductor substrate. The underlayer includes a main polymer having aphotocleavable functional group. A photoresist layer is formed over theunderlayer. The photoresist layer is selectively exposed to actinicradiation, and the selectively exposed photoresist layer is developed toform a photoresist pattern. In an embodiment, the selectively exposingthe photoresist to actinic radiation cleaves the photocleavablefunctional group in the underlayer. In an embodiment, the selectivelyexposing the photoresist to actinic radiation adjusts a glass transitiontemperature (Tg), density, or porosity of the underlayer. In anembodiment, the photocleavable functional group is an oligomer or apolymer. In an embodiment, a number of repeating units of thephotocleavable functional group ranges from 2 to 500. In an embodiment,the photocleavable functional groups are embedded in a backbone of themain polymer, side chain of the main polymer, or cross linker. In anembodiment, the underlayer is an organic polymer or an inorganicpolymer. In an embodiment, the inorganic polymer is a polysiloxane. Inan embodiment, the photocleavable functional group is a polycarbonate ora polysulfone.

Another embodiment of the disclosure is a method of manufacturing asemiconductor device, including forming a photoresist underlayer over asemiconductor substrate. The underlayer includes a main polymer. Aphotoresist layer is formed over the underlayer. The photoresist layerand underlayer to are selectively exposed to actinic radiation. A glasstransition temperature (Tg) is decreased, a density is decreased, or aporosity is increased of a portion of the underlayer selectively exposedto the actinic radiation. The selectively exposed photoresist layer isdeveloped to form a patterned photoresist layer. In an embodiment, adifference in Tg between exposed and unexposed portions of theunderlayer ranges from 1° C. to 150° C. In an embodiment, a differencein density between exposed and unexposed portions of the underlayerranges from 0.1 to 1 g/cm³. In an embodiment, a difference in porositybetween exposed and unexposed portions of the underlayer ranges from 1%to 50%. In an embodiment, the method includes heating the photoresistlayer and the underlayer at a temperature ranging from 50° C. to 150° C.after the selectively exposing the photoresist layer and the underlayerto actinic radiation and before the developing the selectively exposedphotoresist layer.

Another embodiment of the disclosure is a composition, including apolymer, including: a first main polymer chain, a second main polymerchain, and a photocleavable functional group. The first and second mainpolymer chains are linked by a cross linker. The first and second mainpolymer chains are one or more of a polyhydroxystyrene or an inorganicpolymer. The photocleavable functional group is embedded in the first orsecond main polymer chains, embedded in a side chain of the first andsecond main polymer chains, or embedded in the cross linker. In anembodiment, the photocleavable functional group is an oligomer or apolymer. In an embodiment, a number of repeating units of thephotocleavable functional group ranges from 2 to 500. In an embodiment,the inorganic polymer is a polysiloxane. In an embodiment, thephotocleavable functional group is a polycarbonate or a polysulfone. Inan embodiment, the linking polymer includes a plurality of differentphotocleavable functional groups.

Another embodiment of the disclosure is a method of manufacturing asemiconductor device, including forming a first layer over asemiconductor substrate. The first layer includes a main polymer, andfirst layer has a first glass transition temperature, first density, andfirst porosity. A resist layer is formed over the first layer. The firstglass transition temperature is decreased to a second glass transitiontemperature, the first density is decreased to a second density, or thefirst porosity is increased to a second porosity of a first portion ofthe first layer. A first portion of the resist layer is removed. Theremaining second portion of the resist layer after the removing thefirst portion of the resist layer overlies the first portion of thefirst layer having the second glass transition temperature, seconddensity, or second porosity. In an embodiment, a difference in glasstransition temperature between the first glass transition temperatureand the second transition temperature of the first layer ranges from 1°C. to 150° C. In an embodiment, a difference in density between thefirst density and the second density of the first layer ranges from 0.1to 1 g/cm³. In an embodiment, a difference in porosity between the firstporosity and the second porosity of the first layer ranges from 1% to50%. In an embodiment, the main polymer is one or more of apolyhydroxystyrene or an inorganic polymer. In an embodiment, theinorganic polymer is a polysiloxane.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

What is claimed is:
 1. A composition, comprising: a cross linker; afirst main polymer chain; a second main polymer chain; and aphotocleavable functional group, wherein the photocleavable functionalgroup is a polycarbonate or a polysulfone, the photocleavable functionalgroup is embedded in the first or second main polymer chains, embeddedin a side chain of the first and second main polymer chains, or embeddedin the cross linker.
 2. The composition of claim 1, wherein thephotocleavable functional group is an oligomer or a polymer.
 3. Thecomposition of claim 1, wherein a number of repeating units of thephotocleavable functional group ranges from 2 to
 500. 4. The compositionof claim 1, wherein the first and second main polymer chains are one ormore of a polyhydroxystyrene, polyacrylate, polymethacrylate,polyvinylphenol, polystyrene, an inorganic polymer, and copolymersthereof.
 5. The composition of claim 4, wherein at least one of thefirst and second polymer main chains is the inorganic polymer and theinorganic polymer is a polysiloxane.
 6. The composition of claim 5,wherein the polysiloxane includes epoxy groups, amine groups, or thiolgroups.
 7. The composition of claim 4, wherein at least one of the firstand second main polymer chains is a polyhydroxystyrene selected from thegroup consisting of a poly(4-hydroxystyrene), apoly(4-vinylphenol-co-methyl methacrylate) copolymer, and apoly(styrene)-b-poly(4-hydroxystyrene) copolymer.
 8. The composition ofclaim 1, wherein the polymer includes a plurality of differentphotocleavable functional groups.
 9. The composition of claim 1, furthercomprising a solvent.
 10. A composition, comprising: a cross linker or acoupling agent; a first polymer; a second polymer; polycarbonate orpolysulfone photocleavable groups embedded in either the first polymer,the second polymer, or the cross linker, wherein at least one of thefirst polymer or the second polymer is a polyhydroxystyrene,polyacrylate, polymethacrylate, polyvinylphenol, polystyrene, or apolysiloxane.
 11. The composition of claim 10, wherein both the firstpolymer and the second polymer are a polyhydroxystyrene, polyacrylate,polymethacrylate, polyvinylphenol, polystyrene, or a polysiloxane. 12.The composition of claim 10, wherein the polycarbonate or polysulfonephotocleavable groups are in main chains of both the first polymer andthe second polymer.
 13. The composition of claim 10, wherein thepolycarbonate or polysulfone photocleavable groups are in side chains ofboth the first polymer and the second polymer.
 14. The composition ofclaim 10, wherein at least one of the first polymer and the secondpolymer chains is a polyhydroxystyrene selected from the groupconsisting of a poly(4-hydroxystyrene), a poly(4-vinylphenol-co-methylmethacrylate) copolymer, and a poly(styrene)-b-poly(4-hydroxystyrene)copolymer.
 15. The composition of claim 10, comprising the couplingagent, wherein the coupling agent reagent has the following structure:

where R is a carbon atom, a nitrogen atom, a sulfur atom, or an oxygenatom; M includes a chlorine atom, a bromine atom, an iodine atom, —NO₂;—SO₃—; —H—; —CN; —NCO, —OCN; —CO₂—; —OH; —OR*, —OC(O)CR*; —SR*,—SO₂N(R*)₂; —SO₂R*; SOR*; —OC(O)R*; —C(O)OR*; —C(O)R*; —Si(OR*)₃;—Si(R*)₃; or epoxy groups, and R* is a substituted or unsubstitutedC1-C12 alkyl, C1-C12 aryl, or C1-C12 aralkyl.
 16. A composition,comprising: a cross linker; a first polymer; a second polymer;polycarbonate or polysulfone photocleavable groups embedded in eitherthe first polymer, the second polymer, or the cross linker, wherein atleast one of the first polymer or the second polymer is apolyhydroxystyrene, polyacrylate, polymethacrylate, polyvinylphenol,polystyrene, or a polysiloxane, and wherein the cross linker includes

where C is carbon, n ranges from 1 to 15; A and B independently includea hydrogen atom, a hydroxyl group, a halide, an aromatic carbon ring, ora straight or cyclic alkyl, alkoxyl/fluoro, alkyl/fluoroalkoxyl chainhaving a carbon number of between 1 and 12, and each carbon C contains Aand B; a first terminal carbon C at a first end of a carbon C chainincludes X and a second terminal carbon C at a second end of the carbonchain includes Y, wherein X and Y independently include an amine group,a thiol group, a hydroxyl group, an isopropyl alcohol group, or anisopropyl amine group, except when n=1 then X and Y are bonded to a samecarbon C.
 17. The composition of claim 16, wherein both the firstpolymer and the second polymer are a polyhydroxystyrene, polyacrylate,polymethacrylate, polyvinylphenol, polystyrene, or a polysiloxane. 18.The composition of claim 16, wherein the polycarbonate or polysulfonephotocleavable groups are in a main chain of at least one of the firstpolymer and the second polymer.
 19. The composition of claim 16, whereinthe polycarbonate or polysulfone photocleavable groups are in sidechains of at least one of the first polymer and the second polymer. 20.The composition of claim 16, wherein the polycarbonate or polysulfonephotocleavable groups are embedded in the cross linker.